1. Field of the Invention
The present invention relates to a device for interrupting power transmission from an input side to an output side in a friction type one-way clutch.
2. Description of the Prior Art
In a helicopter, for instance, a main transmission system for transmitting power of an engine to a main rotor (a lift rotor) is provided with a clutch, a reduction gear and the like, and in some cases a friction type one-way clutch is employed as the aforementioned clutch.
A friction type one-way clutch in the prior art will be described with reference to FIGS. 7-9.
In these figures, reference numeral 100 designates a clutch housing, and within this clutch housing 100 is rotatably supported an input shaft 110 via bearings 101 and 102. It is to be noted that the bearing 102 is disposed inside an output shaft 114 which will be described later.
The input shaft 110 is cylindrical and an input gear 112 is formed on the outer surface of its one end. This input gear 112 is connected to an engine (not shown) to receive rotation from the engine.
Outside the above-mentioned input shaft 110 is rotatably supported an output shaft 114 as spaced from the input shaft 110. The output shaft 114 is also cylindrical and is supported rotatably with respect to the housing 100 via bearings 103 and 104, but it can rotate independently of the above-mentioned input shaft 110. An output gear 116 is formed on the outer surface of one end of the output shaft 114. This output gear 116 is connected to a drive system for rotating, for instance, a main rotor of a helicopter.
Between the above-mentioned input shaft 110 and output shaft 114 is provided a friction type one-way clutch 120. The structure of the one-way clutch 120 is shown also in FIGS. 8 and 9, in which a cam section 122 and a cam ring section 124 are formed at the outer surface of the input shaft 110 and the inner surface of the output shaft 114. Between these cam section 122 and cam ring section 124 is provided a gap whose width varies in the circumferential direction, and a plurality of rollers 126 and a cylindrical retainer 128 are provided in this gap along the circumferential direction to form the one-way clutch. As shown in FIG. 8, the respective rollers 126 are rotatably accommodated within holding holes formed in the retainer 128.
As shown in FIG. 9(a), if the input shaft 110 rotates in the direction of an arrow, the cam section 122 and the cam ring section 124 would relatively displace in the circumferential direction. Hence, the rollers 126 would frictionally engage the cam section 122 and the cam ring section 124 in a narrower portion of the gap and would become frictionally constrained between these input shaft 110 and output shaft 114. Accordingly, rotation of the rollers 126 is prevented, so that rotation of the input shaft 110 is transmitted to the output shaft 114 via the rollers 126 and the output shaft 114 is rotated in the direction of the arrow integrally with the input shaft 110.
However, if the retainer 128 is moved in the circumferential direction as shown in FIG. 9(b), the retainer 128 would shift the rollers 126 to a wider portion of the gap between the cam section 122 and the cam ring section 124 consequently the rollers 126 are released from constrainment between the cam section 122 and the cam ring section 124, so that the coupling between the input shaft 110 and the output shaft 114 is interrupted and rotation of the input shaft 110 cannot be transmitted to the output shaft 114.
Under a normal condition, a spring 134 is equipped between a spring receiving portion 130 formed on the input shaft 110 and a spring receiving portion 132 formed on the retainer 128. Hence the retainer 128 is pushed in the circumferential direction by this spring 134, and the rollers 126 are pushed towards the narrower portion of the gap between the cam section 122 and the cam ring section 124. Consequently, the clutch is held in an ON state.
As described previously, however, if the end portion of the retainer 128 is pushed in the circumferential direction against the resilient force of the spring 134, then the retainer 128 would rotate, and since the rollers 126 would shift in the circumferential direction, the coupling is released and the clutch is turned to an OFF state.
Means for actuating the retainer 128 in the circumferential direction in the prior art will be described in the following.
That is, at one end of the retainer 128 is formed an extension as shown in FIGS. 7 and 8, and in this extension is formed a cam hole 136 having a triangular window shape as will be apparent from FIG. 8. This cam hole 136 has a cam surface inclined with respect to the circumferential direction and the axial direction. Into the above-mentioned cam hole 136 is inserted a cam bar 138.
The cam bar 138 is engaged with a transmission sleeve 140 via splines, and it is fixedly secured to this transmission sleeve 140 by means of a nut 141.
The transmission sleeve 140 is disposed inside the input shaft 110 and is engaged with the input shaft 110 via splines, and accordingly it is freely movable in the axial direction.
Within the transmission sleeve 140 is slidably inserted a buffer rod 142, and between this buffer rod 142 and the above-mentioned transmission sleeve 140 is provided a coil spring 144.
The other end of the buffer rod 142 is introduced to the inside of an intermediate sleeve 146, which is also disposed inside the input shaft 110 and is made movable in the axial direction by being engaged with the input shaft 110 via splines. The other end of the above-mentioned buffer rod 142 is adapted to butt against one end surface of the intermediate sleeve 146. At an end portion of this buffer rod 142 is fixed a spring receiver 45, and a coil spring 147 is disposed between this spring receiver 145 and the intermediate sleeve 146.
One end of the intermediate sleeve 146 is connected to an actuator shaft 151 via a bearing 148. In other words, although the intermediate sleeve 146 and the actuator shaft 151 would move integrally in the axial direction, relative rotational movement therebetween is allowed by the bearing 148.
The actuator shaft 151 is connected to an electrically-operated actuator, that is, a linear actuator 150. The linear actuator 150 is provided with a motor section, speed reduction gears for slowing down the rotation of the motor section, a screw jack mechanism for transforming the rotational motion slowed down by the reduction gears into linear motion, and the like, although not shown, and it is fixed to the other end of the clutch housing 100. Accordingly, if an electric signal is applied to the linear actuator 150, the actuator shaft 151 would be moved in the axial direction.
In the clutch having the above-described structure if the actuator shaft 151 is moved in the rightward direction as viewed in FIG. 7 by the linear actuator 150, the intermediate sleeve 146 is also moved in the axial direction in a similar manner. The movement in the axial direction of the intermediate sleeve 146 is transmitted to the buffer rod 142, and the movement of this buffer rod 142 is transmitted to the transmission sleeve 140 via the coil spring 144. That is, the transmission sleeve 140 is moved rightwards as viewed in FIG. 7. Then the cam bar 138 fixed to the transmission sleeve 140 also moves likewise in the rightward direction.
Since the cam bar 138 extends into the triangular cam hole 136 formed in the extension of the retainer 128 as will be apparent from FIG. 8, the above-mentioned movement of the cam bar 138 in the axial direction causes the retainer 128 to move in the circumferential direction, that is, to rotate.
More particularly, by the above-mentioned operation of the linear actuator 150 the retainer 128 is actuated in the circumferential direction. Hence as described previously, the retainer 128 shifts the rollers 126 to a wider portion of the gap between the camsection 122 and the cam ring section 124, and consequently, the rollers 126 are released. Therefore, power transmission between the input shaft 110 and the output shaft 114 is interrupted.
It is to be noted that the buffer rod 142 and the coil springs 144 and 147 are provided for the purpose of absorbing impacts of reciprocating motions caused by operation of the linear actuator 150.
In the clutch in the prior art as described above, a motor section, speed reduction gears and a screw jack mechanism or linear actuator 150 is used as a clutch interrupting device, and the buffer rod 142 and the coil springs 144 and 147 for absorbing impacts of reciprocating portions as well as the intermediate sleeve 146 and the transmission sleeve 140 constitute a large number of component parts. The structure is complicated, the route along which power is transmitted in the clutch is complicated, and a lot of labor is necessary for assembly.
Also, because the clutch interrupting device composed of a large number of component parts as described above must be accommodated within the hollow input shaft 110, the component parts must be small and so their mechanical strengths are not great. Also, vibrations of the input shaft would propagate to these members. Hence wear and damage caused by high-speed motion and high-frequency vibration are liable to occur, and so the reliability of the device is poor.
Furthermore, because the bearing 148 is used for transmitting torque generated in the stationary linear actuator 150 to the rotating input shaft 110, the wear-resisting property of this bearing 148 is of great concern, and precision in the centering of the bearing 148 is required.
In addition, in a power transmission system for interrupting a clutch, as a rule, it is necessary that the linear actuator 150 be disposed coaxially with the rod 142. Therefore, the layout of the system is restrictive. For instance, if another driving device or an auxiliary machine is connected to the other end of the clutch housing 100, the illustrated structure cannot be employed, or, in the event that the illustrated structure is employed, another driving device or an auxiliary machine cannot be disposed at the other end of the clutch housing 100.